Pump arrangements for gas-turbine engine fuel systems



Y- 1957 D. H. BALLANTYNE ETAL 2,813,394

PUMP ARRANGEMENTS FOR GAS-TURBINE ENGINE FUEL SYSTEMS Original Filed March 6, 1950 AXIALHOW COMPRESSOR.

United-States Patent PUMP ARRANGEMENTS FOR GAS-TURBINE 1 i ENGINE FUEL SYSTEMS v David Havel'ock Ballan'tyne, Littleo'v'er, David Omrl Davies, Derby, and Desmond Edward Bowns, Notj tinghii'm, En land, assignors to Rolls-Royce Limited, Derby, England, a Britishcompany r Original application March 6, 1950, Serial No. "147,893",

now Patent No. 2,706,888, dated April 26, 1955. Divided and this application October 26, 1953, Serial No. 388,374 fil'aims priority, application Great Britain March 10, 1949 1 Claim. (Claw-45.6)

This application is a divisional of our co-pending United States applica'tion Serial No. 147,893, filed Mareh6, 1950, now U. S. Patent No. 2,706,888, for Pump Arrangements for Gas-Turbine Engine Fuel Systems.

The present invention relates to gas turbine power plant installations of the kind having a gas turbine engine comprising a compressor system, combustion equipment connected to receive air direct from said compressor system, a turbine connected to receive products of combustion direct from said combustion equipment, and reheat combustion equipment connected to the outlet of said turbine to heat the gas exhausted from the turbine and including reheat fuel injectors.

The object of the present invention is to provide a new fuel system for supplying fuel to the reheat fuel injectors.

An embodiment of the invention will now be described With reference to the accompanying drawings in which,

Figure 1 illustrates diagrammatically one fuel system in accordance with the invention,

Figure 2 illustrates a form of air-motor-driven pump suitable for use in the arrangement of Figure 1.

Referring to Figure 1, there is illustrated a gas turbine engine of the jet propulsion type suitable for use in aircraft. The engine comprises a compressor 11 illustrated as an axial-flow compressor, combustion equipment 12, illustrated as comprising a series of separate combustion chambers each containing a fuel injector 16, a turbine 13 and an exhaust assembly 14 leading to a jet pipe 15 in which reheat fuel injectors 25 are located. Air compressed by the compressor 11 is delivered to the combustion equipment 12 where it is heated by fuel injected through the fuel injectors 16. The products of combus tion pass directly to the turbine 13 to drive it and then into the exhaust assembly 14 and jet pipe 15. The turbine drives the compressor by a shaft (not shown) extending centrally through the combustion equipment.

Fuel is delivered into the combustion equipment through the fuel injectors 16 from a manifold 17 which is supplied through a duct 20 from an engine-driven main fuel pump 24 which in this instance is illustrated as being a gear pump.

The drive to the pump 24 is indicated at 24a.

As is well known, the amount of fuel which can be burnt in the combustion equipment 12 is limited by considerations of the allowable temperature for the blades of the turbine 13.

This consideration does not affect the supply of fuel through the reheat fuel injectors 25 since they are downstream of the turbine and the parts with which gas heated by fuel injected through the reheat fuel injectors comes in contact are not highly stressed. It is therefore permissible for the exhaust gas to be at a much higher temperature than the products of combustion entering the turbine and so it is usual for a much larger flow of fuel to be in 2,813,394 Patented Nov. 19, 1957 ICC.

jected through the reheat fuel injectors than is injected into the main combustion equipment.

Fol-example, the maximum fuel supply by the main fuel system to the combustion equipment 12 may be of the order of 600 gallons per hour and this amount will normally be supplied whenever the reheat fuel system is operating. The reheat fuel system on the other hand may for example use approximately 1400 gallons per hour in an engine in which the maximum main fuel supply is 600 gallons per hour. Thus it will be appreciated that the fuel pump of the reheat fuel system has to deal with a much larger quantity of fuel than does the pump 24 of the mainfuel system. The reheat fuel system in the embodiment being described comprises a centrifugal pump 31 which supplies fuel through a pipe line '26 provided with a shueofi. valve 37 to the reheat fuel injectors 25. This reheat fuel pump 31 is driven through a shaft from an impulse airturbine 35. The airt'urbine 35 is supplied with compressed air-through the ducts '23 and 23a from the compressor 11. The air supply to the air turbine 35 is controlled by an air control valve 38 which is operatively connected with the shut-off valve 37 so that fuel cannot be delivered to the reheat fuel injectors 25 except when the pump 31 is being driven by the air motor 35.

In order to deal with the large quantities of fuel (e. g. 1400 gallons per hour as mentioned above) which have to be supplied to the reheat fuel injectors 25, the pump 31 has to have a large capacity and it has been found that a centrifugal pump driven at high speed is eminently suitable.

In the embodiment being described, the pump 31 is driven at a speed of about 10,000 R. P. M.

Fuel is supplied to the inlet of both the pump 31 and the pump 24 by a booster pump 30 which is situated inside the fuel tank 18. The pump 30 delivers through a a conduit 34 to the inlet of the pump 31 and a branch pipe 23 from the conduit 34 leads to the inlet of the pump 24.

The pump 30 may be driven in any convenient manner but it has to be appreciated that when the reheat fuel system is in operation and the main fuel pump 24 is delivering at its full capacity, the pump 30 will have to deal with a total of about 2,000 gallons per hour of fuel, though it does not have to discharge at a high pressure.

Any suitable pumpto meet these requirements may be employed and it may be driven in any suitable manner. It has been found convenient to employ a centrifugal pump for the pump 30 mounted inside the fuel tank and to drive it from an air turbine 32 through a shaft 33. However the requirements for the pump 30 are such that it is preferable to use one with a larger impeller than that of the pump 31 and to drive it at a lower speed say, 1,000 R. P. M.

The air supply to the air turbine 32 is also taken from the compressor 11 through the pipe 23.

One suitable construction of centrifugal pump and air turbine to drive it is shown in Figure 2, the pump being located inside the wall of the fuel tank.

In this figure, the wall of the fuel tank is indicated at and an aperture is provided therein which is closed by a plate 51. The plate 51 has formed on its outer surface and integral with it, an exhaust scroll 52 of an air impulse turbine, the rotor disc 53 of which is carried on a shaft 54 mounted in bearings 55 accommodated centrally of the scroll 52 and in bearings 56 housed in an internal hollow boss 57 on a cover plate 58 of the turbine.

A plate 59 formed with a series of nozzles 60 is located between the cover plate 58 and the rotor disc 53. The space 61 between the plate 59 and the cover plate 58 forms an air distribution chamber for the nozzles 60.

Mounted on the inner surface of the plate 51 by means of; standards 62, there is one part 63a of the casing of a double-entry centrifugal pump, the impeller 64 of which is of the shrouded type. The other part 63b of the casing is secured to the part 63a and carries a conical member 65 forming the inlet'to the upper eye of the impeller. The impeller 64 is secured to an extension ofthe shaft 54 of the turbine rotor disc 53 to rotate therewith. A

flexible metal bellows-type legging 66 is located in a cavity in the plate Sl and is secured at its lower end to the plate. The upper end of the legging 66 carries a washer member bearing on the hub of the impeller 64. The legging 66 acts to prevent leakage of fuel along the shaft 54.

We claim: I I

In a gas turbine power plant installation having a gas turbine engine comprising a compressor system, combustion equipment connected to receive air direct from said compressor system, a turbine connected to receive prodnets of combustion direct from said combustion equipment,.and reheat combustion equipment connected to the outlet of said turbine to heat the gas exhausted from the high-speed centrifugal fuel pump-having an inlet and an outlet, a delivery pipeline connected between the outlet of i said pump and said reheat fuel injectors, a fuel tank located remotely from the engine, a centrifugal booster pump of large capacity compared with said high-speed centrifugal fuel pump, said booster pump having an inlet in direct communication with said tank to draw fuel therefrom and having an outlet, a first air turbine drivingly connected to said booster pump, a fuel connection from the outlet of said booster pump to the inlet of said highspeed pump, a second air turbine drivingly connected with said high-speed centrifugal, pump to drive it at a high speed relative to the speed of rotation of said booster pump, and air ducts between said compressor system and said first and second air turbines to supply compressed air to said air turbines.

References Cited in the file of this patent UNITED STATES PATENTS 2,506,611 Neal et a1. May 9, 1950 2,520,967 Schmitt Sept. 5, 1950 2,551,229 Alford et al May 1, 1951 2,612,020 Grifiith Sept. 30, 1952 2,640,316 Neal June 2, 1953 2,658,330 Carey Nov. 10, 1953 

